Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.97	12.487%	$116.9527	$116.95	$116.95	$117.00
Purchase #2	$199.99	6.162%	$212.3134	$212.31	$212.30	$212.30
Purchase #3	$173.26	10.565%	$191.5649	$191.56	$191.55	$191.60
Purchase #4	$152.30	8.780%	$165.6719	$165.67	$165.65	$165.70
Purchase #5	$105.35	5.483%	$111.1263	$111.13	$111.15	$111.10
Purchase #6	$67.76	7.829%	$73.0649	$73.06	$73.05	$73.10
Purchase #7	$170.82	5.701%	$180.5584	$180.56	$180.55	$180.60
7 purchase totals =	$973.45		$1,051.2525	$1,051.24	$1,051.20	$1,051.40